Heat Exchanger Insert

ABSTRACT

The invention relates to an insert intended to encourage the exchange of heat between a first fluid and a second fluid. The insert includes a concertina-folded plate for the circulation of the first fluid. The plate is intended to come into thermal contact with circulation channels for the second fluid. The plate includes a multiplicity of ridges able to divert the circulation of the first fluid from one direction of flow. The insert has an increasing density of ridges in the direction of flow. The invention also relates to a heat exchange bundle including a plurality of such inserts, as well as a heat exchanger for a cooling circuit comprising such a heat exchange bundle.

The invention relates to an insert for a heat exchanger of a motor vehicle, a heat exchange bundle comprising such an insert and a heat exchanger comprising such a bundle.

It relates in particular to the field of exchangers for the supply of air to an engine of a motor vehicle.

It is known that turbocharged engines can be supplied via an air intake system or via a system for the intake of a mixture of air and exhaust gases collected as they exit from the engine, known as recirculated exhaust gases, the air or the mixture of air and recirculated exhaust gases having been compressed beforehand. Elsewhere in this document, the expression “charge air of the engine” is used to denote both the air coming from an air intake system and the mixture coming from a system for the intake of a mixture of air and recirculated exhaust gases.

For the purpose of cooling the charge air and its density, it is known from the prior art to cool said charge air by means of a heat exchanger, also referred to as a charge air cooler (CAC). Charge air coolers comprising alternatively circuits for the circulation of the charge air and circuits for the circulation of a coolant are known in particular.

In order to increase the thermal exchange between the two fluids, it is known to add inserts, also referred to as turbulators or disruptors, disposed in the charge air circuit. They are present in the form of a rectangular plate concertina-folded in such a way as to form a plurality of corrugations extending in a longitudinal axis. The charge air enters on one side of the insert and exits on the other side, substantially following the direction of the corrugations. The apices of the corrugations are in thermal contact with the coolant circuit. The transfer of heat between the two fluids is encouraged by the additional thermal exchange surface provided by the inserts.

Modifications to the configuration of the inserts allow the thermal exchange to be further reinforced. They involve the creation of disruptions for the purpose of imparting a turbulent flow to the air during the circulation of the flow through the insert.

For example, it is possible to have inserts with louvers on the flanks of the corrugations. The louvers are apertures produced through the material; they are provided with flaps, adjacent to the aperture and oriented transversely to the incident direction of the charge air. Inserts of which the corrugations are divided and are offset transversely one after the other are also known.

However, these modifications have the disadvantage of causing a significant loss of pressure in the circulation of the air through the inserts. As a result, although the thermal transfer increases substantially, the performance of the heat exchanger is regarded as not being satisfactory.

The aim of the invention is to improve the structure of the insert, by restricting the loss of pressure, while maintaining a significant thermal transfer between the fluids. The invention also has as its object an insert intended to encourage the exchange of heat between a first fluid and a second fluid, said insert comprising a concertina-folded plate for the circulation of the first fluid, said plate being intended to come into thermal contact with circulation channels for the second fluid, said plate including a multiplicity of ridges able to divert the circulation of said first fluid from one direction of flow, said insert having an increasing density of ridges in said direction of flow.

In other words, the insert comprises, between the inlet and the outlet, a progressively larger number of elements causing disruptions.

The invention is based on the observation that the ratio between the thermal performance and the loss of pressure is dependent on the flow velocity of the air and its temperature; it is higher in particular at a low flow velocity. It is consequently more useful to have disruptions when the flow velocity has already decreased, that is to say towards the outlet from the insert, rather than at the inlet, where the flow velocity is highest. It is thus possible to reduce the loss of pressure by avoiding causing disruptions at the inlet of the flow of air, while maintaining an effective thermal transfer by providing disruptions at the outlet from the conduit. In fact, the disruptions encourage the thermal exchange by increasing the coefficient of thermal transfer between the fluids. On the other hand, the presence of disruptions at the inlet is of little use since the loss of pressure generated is not very effective. As the fluid progresses in the insert, its flow velocity falls and the ratio between the thermal performance and the loss of pressure increases. A larger presence of disruptions becomes increasingly significant as the fluid circulates in the insert. The density of the ridges is thus increased progressively, according to the invention, in order to provide greater heat exchange efficiency.

According to one aspect of the invention, said plate comprises a plurality of corrugations intended to guide said fluid in the direction of flow, each corrugation being offset, one in relation to the other, in a direction transverse to said direction of flow, in such a way that said ridges are formed by opposed end edges of said corrugations. In other words, the offset between the corrugations causes said ridges to appear in the flow of the fluid arriving from the preceding corrugation. As a result the fluid, guided by the corrugations, is disrupted by the ridges disposed at the junction of two successive corrugations.

According to this aspect of the invention, in order to obtain an increasing density of ridges in the direction of flow of the first fluid, the length of said corrugations is decreasing.

According to different embodiments of the invention, which may be considered together or separately:

-   -   the insert is produced from a single plate,     -   the insert comprises at least two zones, each zone including a         constant density of ridges,     -   the thermal exchange surface of the insert is substantially the         same for each of said zones,     -   said corrugations of each of said zones are of the same length,     -   the first zone, in the direction of flow, has only a single         corrugation,     -   the corrugations are offset by a distance that is substantially         equal to half of the pitch of the corrugation,     -   the length of the shortest corrugations lies in the range         between 0.5 and 1.5 mm,     -   the plate has a thickness which lies in the interval from 0.05         to 0.3 mm,     -   each zone has a length which lies in the interval from 10 to 50         mm,     -   the corrugations have a pitch which lies in the interval from         0.5 to 10 mm,     -   the corrugations have a height which lies in the range from 1 to         15 mm,     -   the insert is produced by the pressing, molding or stamping of a         metal plate.

The invention also has as its object a heat exchange bundle comprising a plurality of inserts as described previously.

According to different embodiments of the invention, which may be considered together or separately:

-   -   the heat exchange bundle comprises two blades forming a pair,         said pair defining a channel for the circulation of the first         fluid in which one of said inserts is situated, and two blades         of two different pairs defining a channel for the circulation of         the second fluid,     -   the heat exchange bundle is configured so that the second fluid         circulates in a flow perpendicular to the direction of flow,     -   the channel for the circulation of the second fluid comprises a         plurality of passages, permitting the second fluid to change         direction from one passage to the other,     -   the bundle comprises as many passages as insert zones, each         passage for the second fluid corresponding to an insert zone.

The invention also has as its object a heat exchanger comprising a heat exchange bundle as described previously. This may be, for example, a cooler for charge air, in particular a cooler for charge air in which the charge air is cooled with the help of a coolant.

The invention will be better appreciated in the light of the following description, which is provided here only as an indication, and which is not meant to limit the invention, accompanied by the drawings attached hereto, in which:

FIG. 1 illustrates, in perspective, an example of an insert according to the invention,

FIG. 2 illustrates schematically a view in transverse section of a corrugation of the insert in FIG. 1,

FIG. 3 illustrates, in perspective, a heat exchanger comprising inserts according to the invention.

Identical numerical references are used below to designate identical or analogous elements.

As illustrated in the FIG. 1, the invention relates to an insert 1 intended to encourage the exchange of heat between a first fluid and a second fluid. It comprises a plate 2 concertina-folded in such a way that the thermal exchange surface with the first fluid is large. Said first fluid, circulating along the insert 1 in a direction of flow 5, is intended to be placed in thermal contact with circulation channels, which are not represented in this drawing, for the second fluid.

The first fluid is a gas, for example, in particular the charge air for a turbocharged engine of a vehicle, which must be cooled with the help of a second heat transfer fluid. Advantageously, the second fluid is a liquid, in particular an antifreeze liquid, in particular a mixture of water and glycol, obtained from a low-temperature cooling loop of the vehicle.

The air enters on one side, referred to as the inlet 7 of the insert, at a high temperature, before being cooled, in contact with the plate 2, as far as the outlet 8 from the insert on the other side.

Said plate 2 includes a multiplicity of ridges 9, able to divert the circulation of said first fluid from the direction of flow 5. The ridges 9 cause disruptions in the flow of the air, which encourage the thermal transfer between the two fluids, via the surface 6 of the insert 1. According to the invention, the insert 1 has an increasing density of ridges 9 in the direction of flow 5, in order to prevent an unnecessary loss of pressure at the inlet 7 of the insert, while increasing the coefficient of thermal exchange at the outlet 8.

For this purpose, the insert in this case comprises a plurality of corrugations 10 intended to guide the air in the direction of flow 5. Each corrugation 10 defines a series of parallel channels 30 in which the first fluid circulates in said direction of flow. Each corrugation includes a series of parallel folds 11, separated by apices 32, intended to come into contact with the circulation conduits for the second fluid.

The ridges 9 are formed by the edges referred to as being transverse 34, at opposite ends of said corrugations 10, and perpendicular to a longitudinal direction of extension of said apices 32.

In other words, a corrugation 10 has, on its transverse edges 34, a multiplicity of ridges 9 disrupting the circulation of the air. Said ridges 9 correspond in particular to each opposite end of the folds 11, in said longitudinal direction of extension of said apices 32. Said transverse edges 34 may have a sinusoidal shape, in the form of castellations, triangular or any other recurring form, or not.

FIG. 2 depicts a view in section of a corrugation 10, in which a series of folds 11 and apices 32 can be seen, as well as the pitch p and the height h of one of the corrugations 10, being respectively equal to a period of said corrugation 10 and to the distance between two neighboring apices 32. Unlike the corrugations provided with louvers, the folds 11 in this embodiment are smooth.

With further reference to FIG. 1, it is clear that the plate 2 forming the insert 1 is rectangular in this case, in such a way that said direction of flow 5 is parallel to two edges 15 of said plate, which we will designate as parallel edges, and perpendicular to the two others, which we will designate as inlet edges 16 and outlet edge 17.

The corrugations 10 are disposed one after the other, with two of their transverse edges 34 in contact. Each corrugation 10 is offset, one in relation to the other, in a direction transverse to the direction of flow 5. This offset causes the ridges 9 of the transverse edge 34 of the following corrugation to appear in the circulation of the fluid arriving from the preceding corrugation. It does not modify the deployed width of the corrugation, that is to say the deployed dimension of the insert in the direction perpendicular to said direction of longitudinal extension of said apices 32.

Advantageously, the profiles of the corrugations 10 are identical, two by two, the corrugations 10 being offset in relation to one another and the apices 32 of the corrugations 10 being collinear. In addition, the pitch p of the corrugations is the same for all the corrugations 10. In this way, the choice and the adjustment of the density is easier to realize.

The length 13 of said corrugations 10 is decreasing in the direction of flow 5. An increasing density of ridges is obtained as a result. In fact, since the corrugations 10 are offset one after the other, the density of the ridges increases if the length 13 of the corrugations 10 reduces.

The insert may comprise a plurality of zones 18, each having a constant density of ridges. In this case, this is manifested as zones 18 of which the corrugations are of identical dimensions, in particular the length l. Thus, the greater the number of corrugations 10 in a zone 18, the higher the density of the ridges 9.

Because the disruptions are less effective at the start of the insert, the first zone 19 is provided with only a single corrugation 10. In other words, the first zone 19 has a zero density of ridges.

In the example in FIG. 1, the insert 1 has four zones 18 with different densities. As already mentioned, the first 19 has only a single corrugation 10. The second comprises ten corrugations of the same length l, the third having twenty, and the fourth having thirty thereof.

The insert 1 is made from a single plate 2, that is to say that the zones 18 and the corrugations 10 are obtained from material one from the other. The use of assembly processes for zones 18 which could have been realized separately is thus avoided.

In addition, in a given zone, the thermal exchange surface 6 is substantially the same for the corrugations of said zone, irrespective of the number of corrugations 10.

Preferably, the offset 20 between the corrugations 10 has a value substantially equal to half of the pitch p of the corrugation 10. This characteristic permits centering of the ridges 9 in the middle of the flow of air exiting from the folds 11 of the preceding corrugation, so that the disruptions are larger and more effective.

The zones 18 in this case have the same length in said direction of longitudinal extension of the apices 32. The thermal exchange surface 6 is thus substantially the same for each of said zones.

In the example in FIG. 1, the insert has a height which lies in the interval from 1 to 15 mm, in particular about 5 mm. It comprises four zones 18 having a length lying in the range from 10 to 50 mm, in particular about 30 mm. The first zone 19 has a length of corrugation of about 30 mm, while the second zone has corrugations having a length of about 3 mm, that of the third being about 1.5 mm and that of the fourth being about 1 mm.

According to another embodiment, not illustrated here, the insert 1 comprises a corrugation provided with louvers forming said ridges. More precisely, the flaps of the louvers have ridges playing the role of a disruptor. The louvers are present in an increasing number between the inlet and the outlet of the insert, in order to achieve an effect similar to that of the preceding embodiment. In this embodiment, the folds of the corrugations are not smooth, as a result of the presence of the louvers.

As illustrated in FIG. 3, the invention likewise relates to a heat exchange bundle 21 comprising a plurality of inserts 1. The first fluid F1, as it enters the bundle, is divided into a plurality of flows, each passing into an insert.

In an advantageous manner, the heat exchange bundle 21 comprises a plurality of blades 22, 23, forming a pair, said pair defining a channel for the circulation 25 of the first fluid F1. The inserts 1 are disposed in each channel 25 and are bordered by the blades 22, 23 of the pair. They are secured to the blades 22, 23 by the apices of the folds 11 of the corrugations 10 and act as a thermal bridge between the two fluids.

The second fluid F2 circulates in circulation channels 28 formed by the blades 23, 26 of two different pairs. Said second fluid F2 makes its way into the bundle via a pipe 36 and exits via a pipe 38. It circulates between the pairs of plates through stampings, not visible here, formed in said plates and connecting between them the circulation channels for said second fluid.

The bundle comprises, as an alternative, circulation channels 25 for the charge air and circulation channels 28 for the coolant, being superposed one above the other. The bundle is thus formed from a stack of plates and inserts.

Preferably, the heat exchange bundle 21 is configured in such a way that the second fluid F2 circulates in the channels formed between the plates in a flow perpendicular to the direction of flow 5. The channel for the circulation 28 of the second fluid comprises, in particular, a circuit in the form of a coil, not visible here, formed from a plurality of passages arranged between the blades 23, 26. Each passage is defined as a conduit element, passing through the bundle 21 from one transverse edge 40 to the other 42. The blades thus comprise, in the area of each passage, a zone for the exchange of heat between the first fluid and the second fluid, said blades being configured in such a way that the liquid changes its direction of circulation between each passage.

Advantageously, the bundle will have as many passages in the blades as there are zones 18 of inserts 1, in such a way that each passage for the second fluid corresponds to an insert zone 18. This arrangement ensures a better distribution in the exchange of heat.

The inserts 1 are preferably assembled to the blades 22, 23, 26 by brazing the material, based on aluminum or an aluminum alloy, of the constituent components of the bundle.

The invention further relates to a heat exchanger. Said exchanger comprises a bundle 21, as represented in FIG. 3. It comprises in addition, for example, inlet boxes and/or outlet boxes for the first fluid, not represented here. 

1. An insert intended to encourage the exchange of heat between a first fluid and a second fluid, the insert comprising a concertina-folded plate for the circulation of the first fluid, the plate for coming into thermal contact with circulation channels for the second fluid, the plate including a multiplicity of ridges able to divert the circulation of the first fluid from one direction of flow, the insert having an increasing density of ridges in the direction of flow.
 2. The insert, as claimed in claim 1, in which the plate comprises a plurality of corrugations intended to guide the fluid in the direction of flow, each corrugation being offset, one in relation to the other, in a direction transverse to the direction of flow in such a way that the ridges are formed by opposed end edges of the corrugations, the length of the corrugations decreasing in the direction of flow.
 3. The insert, as claimed in claim 2, in which the corrugations are offset by a distance substantially equal to half of a pitch of the corrugation.
 4. The insert, as claimed in claim 2, formed from one and the same said the concertina-folded plate.
 5. The insert, as claimed in claim 2, further comprising at least two zones, each zone including a constant density of ridges.
 6. The insert, as claimed in claim 5, in which the corrugations of each of the zones are of the same length.
 7. The insert, as claimed in claim 5, in which a first zone, in the direction of flow, has only a single corrugation.
 8. The insert, as claimed in claim 6, in which the length of a shortest corrugations lies in the range between 0.5 and 1.5 mm.
 9. The insert, as claimed in claim 5, in which each zone has a length from 10 to 50 mm.
 10. A heat exchange bundle comprising a plurality of inserts as claimed in claim
 1. 11. The heat exchange bundle, as claimed in claim 10, comprising, two blades forming a pair, the pair defining a channel for the circulation of the first fluid in which one of the inserts is situated, and two additional blades forming another pair defining a channel for the circulation of the second fluid.
 12. The heat exchange bundle, as claimed in claim 11, in which the heat exchange bundle is configured so that the second fluid circulates in a flow perpendicular to the direction of flow.
 13. The heat exchange bundle as claimed in claim 11, in which the channel for the circulation of the second fluid comprises a plurality of passages, permitting the second fluid to change direction from one passage to the other.
 14. The heat exchange bundle, as claimed in claim 13, further comprising at least two zones, each zone including a constant density of ridges with the heat exchange bundle comprising as many passages as zones, with each passage of the second fluid corresponding to one of the zone.
 15. A heat exchanger comprising a heat exchange bundle as claimed in claim
 10. 16. The insert, as claimed in claim 3, formed from the concertina-folded plate.
 17. The insert, as claimed in claim 3, further comprising at least two zones, each zone including a constant density of ridges. 